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newwave

Tue Oct 14 2008, 10:47PM

Registered Member #1758 Joined: Tue Oct 14 2008, 09:46PM
Location: noth eastern usa
Posts: 7

I am working on a project that that I've been researching and fiquered it time for some help.
Here ae the project requirements:
#1 requires a massive amount of amps the more the merryer, and lowest voltage output as passible.
#2 the current needs to be, adjustable rate of current on/off /on /off

what circuites I believe I need to build in order:
battery charger
battery
Dc to Ac converter
transformer
Ac to Dc converter
voltage multiplyer
pulse width modualator
load

1st question: do I have all the circuits nessary, or to many, and are they in the right order.
any help or sugestions will be greatly apreciated thanks, sincerly Newwave

Shaun

Tue Oct 14 2008, 11:09PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

It would really help to know what you are using this for since "a massive amount of amps" is a HUGE range. Other than that, you list will work but you must switch "AC to DC converter" and "voltage multiplier" since a voltage multiplier needs AC.

But why are you using a voltage multiplier if you want the lowest output voltage possible? And must it be battery powered?

rp181

Tue Oct 14 2008, 11:17PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

same as shaun, and more like this:
battery charger
battery
(you can replace those 2 with mains, recetified)
voltage doubler if using mains (you can use thinner wire on xformer)
Pulse width modulator (TL494 to create AC)
xfmer
recetifier
filter cap

You do not need the PWM at the end, if its in the beginning, then it will be easier then getting an IGBT to handle high currents.

newwave

Tue Oct 14 2008, 11:51PM

Registered Member #1758 Joined: Tue Oct 14 2008, 09:46PM
Location: noth eastern usa
Posts: 7

shaun and rp181
thanks for the replys it's greatly appreciated.
I was using the voltage multiplyer thinking it might increase the amps as well, I am unsure.
the load can be Ac or Dc, but the source has to be a 12v or 24v battery.
massive amount of amp = I would like to produce as much as possible cost of course is a factor my total for all circuits is 600 - charger, battery and, load

so going(
charger
battery
dc to ac converter
voltage doubler
pulse width modulator
transformer
recetifier( if I go with a dc load?)
filter cap
) should be the way to go

[Edit: Double post]

rp181

Wed Oct 15 2008, 02:41AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

voltage double should be before dc to ac converter. Also, the pulse width modulator IS the dc to ac converter, steve ward's CCPS has a good example of this.

newwave

Wed Oct 15 2008, 04:19AM

Registered Member #1758 Joined: Tue Oct 14 2008, 09:46PM
Location: noth eastern usa
Posts: 7

rp181,
Thank you so very much for claring up the curcuit arrangement for me. thanks for the tip as well, I will check out steve ward's ccps

Dr. Dark Current

Wed Oct 15 2008, 04:49PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

rewind a MOT with a single turn of as big as possible copper bar/litz wire, it will give you just under a volt at 3000-4000A. Not sure how much current you need though and for how long, the MOT will work just a few tens of seconds at this current...

newwave

Sun Oct 19 2008, 03:08AM

Registered Member #1758 Joined: Tue Oct 14 2008, 09:46PM
Location: noth eastern usa
Posts: 7

dr kilovolt sorry I have not been online for a couple of days, thanks for the sugestion. the amperage is a decent amount, but i need to be able to use this for very long periods of time. if only there was a way to keep the mot cool.

does anyone have or know of a xformer were it can constantly give 2500A with 1to 2V s. for that would be perfect for my needs. thanks sincerly newwave

Dr. Slack

Mon Oct 20 2008, 07:13AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

I'm not certain that "12v or 24v battery powered" is consistent with "need to be able to use this for very long periods of time".

When you want to provide a a load with 1000s of amps, then the largest problem is usually getting the resistance of the leads down such that most of your precious converted power ends up in the load rather than the leads. The drop across rectifiers becomes prohibitive too when load voltages fall.

I'm sure most of us could help you more if we had an idea of what your load was. AC or DC suggests heating, besides which <1v rules out electrolysis.

If you can build the load actually as part of a transformer secondary, then that eliminates the leads. Bearing heaters work like this, the bearing itself works as a short-circuited turn as part of a transformer. Even looping a welder lead through the transformer to make a secondary incurs a huge mohm or so series resistance which dominates the load resisitance.

Running the load AC has the advantage that no rectifiers are needed in the 1v part of the circuit, the control devices all operate at the higher voltage.

With DC output from a relatively low voltage 12v DC supply, the thing that occurs to me is to parallel up as many current-output buck converters as you need to get the output current, with synchronous rectification of course. There are chips available for doing polyphase 1.2v 100A supplies for CPUs, these typically run 10-20A per leg. Being for commercial PCs, they are relatively cheap, so paralleling N of them may be practical. Have a look at the Max5065 at maxim-ic.com, dual phase, 12-24v input. Linear, International Rectifier have some as well, but maxim have policy of pushing samples at you, rather than having to be cajoled. Parallel has several advantages, you can prototype at low power and cost, then scale up when you're happy, if one brick fails you only lose 10% of your output.

Bored Chemist

Mon Oct 20 2008, 05:15PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

newwave wrote ...

does anyone have or know of a xformer were it can constantly give 2500A with 1to 2V s. for that would be perfect for my needs. thanks sincerly newwave

There are not many things that you can put that kind of power into continuously.
Really, some idea of what you are trying to do would help a lot here.
Anyway, have you looked into homoplar generators - not normally continuous, but they could be run that way.

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